A webbing winding device disclosed in JP Laid-open Patent Publication No. 2004-74882 includes an insertion hole at its spool main body. The insertion hole divides the spool into two parts: a large-sized part that includes a rotation shaft of the spool; and a small-sized part that does not include the rotation shaft. A recessed part is provided at the periphery of the large-sized part.
A webbing goes out from one of sides of the insertion hole along the periphery of the large-sized part on the spool main body in a webbing-winding direction and reaches the inside of the recessed part where a webbing stopper shaft connects the webbing to the recessed part. The recessed part is located to form an approximately 35-degree angle in the webbing winding direction with reference to an insertion directional line of the insertion hole.
JP Laid-open Patent Publication No. 2004-74882 as conventional art also discloses that one of openings provided at the spool is made wider than the insertion hole so as to fix the webbing stopper shaft there.
In JP Laid-open Patent Publication No. 2004-74882, the webbing coupled with the webbing stopper shaft is fixed at a position where the webbing is taken up by approximately 35 degrees in the webbing-take-up direction through the insertion hole. Accordingly, even when the webbing is intended to be fully pulled out, a little part of the webbing remains as being taken up in the spool. Therefore, intensity can be assured by making the tensile force on the webbing disperse. In view of effective use of a webbing, existence of unused part thereof is problematic.
Further, attachment of the webbing to the take-up drum requires a series of complicated processes as follows: firstly, the webbing is pulled out from one of openings of the insertion hole; next, an end portion of the webbing is folded so as to surround the webbing stopper shaft; and the folded end portion of the webbing with surrounding the webbing stopper shaft is fitted in a concave portion formed on an outer periphery of the large-sized part.
In JP Laid-open Patent Publication No. 2004-74882, the stopper shaft gets engaged with one of the openings of the insertion hole. Therefore, there is no part to be taken up until the front end of the webbing reaches the stopper shaft. There is no part of the webbing which is not included in the pulled-out length of webbing. Further, the folded end portion of the webbing with surrounding the webbing stopper shaft does not need fitting in the concave portion formed on an outer periphery of the large-sized part. However, since the stopper shaft is positioned at one of the openings of the insertion hole, tensile force of the webbing directly works on the stopper shaft when the webbing is fully pulled out. The spool disclosed in the background art is made of metal such as aluminum of which load bearing is poor. Therefore, there arises a fear that the spool itself cannot bear the tensile force working on the stopper shaft. That is, there arises the fear that the insertion hole is forcedly widened as much as the stopper shaft may slip out. This is problematic because strength of an attachment portion when the webbing is fully pulled out (termed as attachment-portion strength) may not be ensured.